A machine type communication terminal can be categorized into a low priority terminal as compared to the normal terminal such as smartphone according to the configuration of the operator. If network overload occurs, the data generated by the low priority terminals are classified into low priority data entirely.
Accordingly, if a low priority terminal attempts network connection or data transmission, the network sets a backoff timer for the corresponding terminal and allows, when the backoff timer expires, the terminal to connect to the network or transmit data. That is, when the network overload occurs, the network restricts the attachment or data transmission of the low priority terminal first.
The data transmission of the low priority terminal is restricted to emergency call placement only. In order to place the emergency call, the terminal or the network has to be able to recognize the emergency call. That is, if the user places an emergency call, the modem of the terminal identifies the emergency call and sends the network an explicit emergency call indicator. Accordingly, the network can recognize the emergency call request from the terminal and allows the emergency call to be made.
Meanwhile, there may be a case where the low priority terminal attempts to transmit to the network a normal priority data which is generated in response to a request of an application but not in an emergency call situation. Such a situation is likely to occur at a machine type terminal.
A vending machine is classified into a low priority terminal which reports sales figures to the management server 12 times a day. The sales report transmitted by the vending machine is classified into low priority data and thus a backoff timer is set in the network overload situation. However, it is necessary to classify the information on the goods out of stock or equal to or less than a predetermined amount into normal priority data such that the network allows for the delivery of this normal priority data.
However, the aforementioned current technology cannot transmit the normal priority data of the low priority terminal with the exception of the emergency call. That is, the low priority terminal does not know whether it is allowed for transmitting normal priority data and, even though the normal data transmission is allowed, there is no way of indicating whether the transmission data has low or normal priority.